Process for preparing mixed carbonates which may comprise hydroxide(s)

ABSTRACT

A process for batchwise preparation of carbonates of at least two transition metals which may comprise hydroxide(s) of the corresponding transition metals, which comprises combining at least one aqueous solution comprising at least two transition metal salts having cations of at least two different transition metals overall with at least one solution of at least one carbonate or hydrogencarbonate of at least one alkali metal or ammonium, 
     introducing a stirrer power of at least 0.25 W/l, 
     and keeping the reaction volume essentially constant during the admixing with alkali metal (hydrogen)carbonate by removing liquid phase while adding solution of alkali metal (hydrogen)carbonate or alkali metal hydroxide.

The present invention relates to a process for batchwise preparation of carbonates of at least two transition metals which may comprise hydroxide(s) of the corresponding transition metals, which comprises

combining at least one aqueous solution comprising at least two transition metal salts having cations of at least two different transition metals overall with at least one solution of at least one carbonate or hydrogencarbonate or hydroxide of at least one alkali metal or ammonium, introducing a stirrer power of at least 0.25 W/l, and keeping the reaction volume essentially constant during the admixing with alkali metal (hydrogen)carbonate by removing liquid phase while adding solution of alkali metal (hydrogen)carbonate or alkali metal hydroxide.

Secondary batteries, accumulators or “rechargeable batteries” are just some embodiments by which electrical energy can be stored after generation and utilized (used) as required. Owing to the significantly better power density, there has in recent times been a move away from the water-based secondary batteries toward development of those batteries in which the charge transport is accomplished by lithium ions.

The electrode material is of crucial significance for the properties of a lithium ion battery. Lithium-containing mixed transition metal oxides have gained particular significance, for example spinels and layered mixed oxides, especially lithium-containing mixed oxides of nickel, manganese and cobalt; see, for example, EP 1 189 296. However, not only the stoichiometry of the electrode material is important, but also other properties such as morphology and surface properties.

For preparation of corresponding mixed oxides, a two-stage process is generally employed. In a first stage, a sparingly soluble salt of the transition metal(s) is prepared by precipitating it from a solution, for example a carbonate or a hydroxide. This sparingly soluble salt is in many cases also referred to as a precursor. In a second stage, the precipitated salt of the transition metal(s) is mixed with a lithium compound, for example Li₂CO₃, LiOH or Li₂O, and calcined at high temperatures, for example at 600 to 1100° C.

Existing lithium ion batteries still have potential for improvement, particularly with regard to the energy density. For this purpose, the cathode material should have a high specific capacity. In addition, it is advantageous when the cathode material can be processed in a simple manner to give electrode layers of thickness from 20 μm to 100 μm, which should have a high density in order to achieve a maximum energy density (per unit volume).

WO 2009/024424 discloses a process for preparing basic transition metal hydroxides, which consists of three steps. These can be characterized as follows:

-   -   a) providing at least one first and a second reactant solution,     -   b) combining at least the first and second reactant solutions in         a reactor and obtaining a homogeneously mixed reaction zone with         a specific mechanical power input of at least 2 watts/liter and         obtaining a product suspension consisting of insoluble product         and a mother liquor, oversaturated by establishment of an         alkaline excess, having a pH of 10 to 12,     -   c) partially removing the mother liquor from the precipitated         product to establish solids contents of at least 150 g/l in the         suspension by means of clarifying elements or filter elements.

However, introduction of major amounts of mechanical energy into large volumes of solutions or suspensions is difficult in apparatus terms.

It was therefore an object of the present invention to provide batteries which have a maximum energy density per unit volume. More particularly, it was therefore an object of the present invention to provide starting materials for batteries which have a maximum energy density per unit volume. It was a further object of the present invention to provide a process by which suitable starting materials for batteries can be produced.

Accordingly, the process defined at the outset has been found.

The process described hereinafter for preparation of carbonates of at least two transition metals which may comprise hydroxide(s) of the corresponding transition metals is also referred to in the context of the present invention as process according to the invention for short.

The process according to the invention relates to the preparation of carbonates of at least two transition metals. In the context of the present invention, “carbonates” includes not just stoichiometrically pure carbonates but also basic transition metal carbonates, and more particularly compounds which, as well as transition metal ions and carbonate ions, also comprise anions other than carbonate ions, for example oxide or hydroxide ions, and/or cations other than transition metal cations, especially alkali metal ions. Preferred alkali metal ions are potassium and especially sodium ions. The molar proportions of anions other than carbonate ions or hydroxide ions and of cations other than transition metal cations need not be identical.

Carbonate of at least two transition metals which my comprise the hydroxide(s) of the corresponding transition metals can also be called “transition metal carbonate” hereinafter.

Transition metal carbonate may comprise mixed salts or mixtures of several different salts. In one embodiment of the present invention, transition metal carbonate comprises hydroxide carbonates with ordered or unordered or partially ordered distribution of the hydroxide ions in the crystal lattice. In many embodiments, transition metal carbonates are amorphous in the X-ray diffractogram.

In one embodiment of the present invention, transition metal carbonate comprises 0.01 to 45 mol %, preferably 2 to 30 mol %, of anions other than carbonate ions, based on the total number of anions in the transition metal carbonate.

In one embodiment of the present invention, transition metal carbonate comprises 4 to 35 mol %, preferably 8 to 20 mol %, of hydroxide ions, based on the total number of anions in transition metal carbonate.

In one embodiment of the present invention, transition metal carbonate comprises 0.01 to 10 mol %, preferably 0.1 to 6 mol %, of cations other than transition metal cations, based on the content of transition metal cations in the transition metal carbonate.

In one embodiment of the present invention, transition metals are selected from Cr, V, Mn, Ni, Fe, Co, Zn, Ti, Zr and mixtures of one or more of the above with one another or with alkali metal, aluminum or magnesium, preferably from mixtures of Ni, Mn, Co and optionally one or more further metals selected from alkali metal, aluminum and magnesium.

In one embodiment of the present invention, transition metal carbonate has the general formula (I)

M(CO₃)_(b)O_(c)(OH)_(d)A_(m)B_(e)X_(f)  (I)

in which the variables are each defined as follows:

-   -   M is one or more transition metals, for example Ni, Mn, Co, Fe,         Cu, Zn, Ti, Cr, the transition metal(s) preferably being present         in the +2 oxidation state, preferably two to four transition         metals, more preferably three transition metals, especially         combinations of nickel, manganese and cobalt,     -   A is potassium or preferably sodium,     -   B is one or more metals of groups 1 to 3 of the Periodic Table,         excluding sodium and potassium,     -   X is halide, sulfate, phosphate, nitrate or carboxylate,         preferably C₁-C₇-carboxylate, especially benzoate or acetate,     -   b is in the range from 0.75 to 0.98,     -   c is in the range from zero to 0.50, preferably 0.30,     -   d is in the range from zero to 0.50, preferably 0.30,         -   where the sum of (c+d) is in the range from 0.02 to 0.50,             preferably 0.30,     -   e is in the range from zero to 0.1, preferably 0.05,     -   f is in the range from zero to 0.1, preferably 0.05,     -   m is in the range from 0.002 to 0.1, preferably 0.05.

The process according to the invention is operated batchwise. “Batchwise” is intended to include those procedures in which one or more reactants are not added until during the reaction. This is also intended to include those procedures in which small samples, called aliquots, are taken during the reaction, for example for quality control. Moreover, this is also intended to include those procedures in which one or more by-products, optionally together with water, are removed from the reaction mixture. Moreover, this is also intended to include those procedures in which the proportion (in g/l) of transition metal carbonate increases over the course of the reaction in the reaction vessel over a prolonged period, for example over a period of at least 2 hours, preferably at least 5 hours, and, for example, up to 50 hours.

In another variant of the process according to the invention, batchwise processes are understood to mean those which are performed semicontinuously, avoiding the steady state. For example, it is possible that reactants are added continuously, while removing one or more by-products from the reaction mixture, optionally together with water, then stopping or slowing the addition of reactants and removing transition metal carbonate and then commencing again with the addition of reactants.

The process according to the invention is preferably performed in a stirred vessel, for example in a batchwise stirred tank. The stirred tank may have installations and/or additions, especially installations or additions for solid/liquid separation. Examples of suitable additions for solid/liquid separation are hydrocyclones, lamellar clarifying apparatus, sedimenters, countercurrent classifiers, centrifuges, units for inverse filtration and combinations of the aforementioned apparatuses, especially sedimenters, lamellar clarifiers, centrifuges and units for inverse filtrations.

Performance of the process according to the invention proceeds from at least one aqueous solution comprising at least two transition metal salts having cations of at least two transition metals overall, preferably of at least three transition metals.

In the context of the present invention, aqueous solution of at least two transition metal salts with cations of at least two transition metal salts altogether is also referred to as aqueous solution of transition metal salts for short.

Aqueous solution of transition metal salts may comprise at least two transition metal salts, preferably two or three transition metal salts, especially salts of two or three transition metals. Suitable transition metal salts are especially water-soluble salts of transition metals, i.e. salts which have a solubility of at least 25 g/l in distilled water, preferably at least 50 g/l, determined at room temperature. Preferred transition metal salts, especially salts of nickel, cobalt and manganese, are, for example, carboxylic salts, especially acetates, and also sulfates, nitrates, halides, especially bromides or chlorides, of transition metals, the transition metals preferably being present in the +2 oxidation state. Such an aqueous solution of transition metal salts preferably has a pH in the range from 2 to 7, more preferably in the range from 2.5 to 6.

Suitable transition metals are, for example, the transition metals of the first period, and also zirconium and molybdenum. Preference is given to V, Ni, Mn, Co, Fe, Zn, Zr, Cr and Ti. Preference is given to selecting mixtures of at least two of the aforementioned transition metals, more preferably of at least three or of at least two of the aforementioned transition metals with magnesium, aluminum or calcium. Very particularly preferred transition metals are combinations of Ni, Co and Mn.

In one embodiment of the present invention, it is possible in accordance with the invention to effect doping with a total of up to 2% by weight of metal ions other than the rest of the transition metals, selected from cations of Na, K, Rb, Cs, alkaline earth metal, Ti, V, Cr, Fe, Cu, Ag, Zn, B, Al, Zr, Mo, W, Nb, Si, Ga and Ge, preferably with a total of up to one % by weight, based on overall compound (I). In another embodiment of the present invention, inventive materials are not doped with other metal ions.

“Doping” shall be understood to mean that, in the course of preparation of inventive materials, in one or more steps, at least one compound having one or more cations selected from cations of Na, K, Rb, Cs, alkaline earth metal, Ti, V, Cr, Fe, Cu, Ag, Zn, B, Al, Zr, Mo, W, Nb, Si, Ga and Ge is added. Impurities introduced by slight contaminations of the starting materials, for example in the range from 0.1 to 100 ppm of sodium ions, based on the inventive starting material, shall not be referred to as doping in the context of the present invention.

In one embodiment of the present invention, it is possible to proceed from an aqueous solution of transition metal salts which, as well as water, comprises one or more organic solvents, for example, ethanol, methanol or isopropanol, for example up to 15% by volume, based on water. Another embodiment of the present invention proceeds from an aqueous solution of transition metal salts which comprises less than 0.1% by weight, based on water, or preferably no organic solvent.

In one embodiment of the present invention, aqueous solution of transition metal salts used comprises ammonia, ammonium salt or one or more organic amines, for example methylamine or ethylenediamine. Ammonia or organic amines can be added separately, or they can be formed by dissociation of complex salts of transition metal salt in aqueous solution. Aqueous solution of transition metal salts preferably comprises less than 10 mol % of ammonia or organic amine, based on transition metal M. In a particularly preferred embodiment of the present invention, aqueous solution of transition metal salts comprises measurable proportions neither of ammonia nor of organic amine.

Preferred ammonium salts may, for example, be ammonium sulfate and ammonium sulfite.

Aqueous solution of transition metal salts may have a total concentration of transition metals in the range from 0.01 to 5 mol/l of solution, preferably 1 to 3 mol/l of solution.

In one embodiment of the present invention, the molar ratio of transition metals in aqueous solution of transition metal salts is matched to the desired stoichiometry in the cathode material or mixed transition metal oxide. It may be necessary to take into account the fact that the solubilities of different transition metal carbonates or transition metal hydroxides may be different.

Aqueous solution of transition metal salts may, as well as the counterions of the transition metal salts, comprise one or more further salts. These are preferably those salts which do not form sparingly soluble salts with M, or hydrogencarbonates of, for example, sodium, potassium, magnesium or calcium, which can cause precipitation of carbonates when the pH is altered.

In another embodiment of the present invention, aqueous solution of transition metal salts does not comprise any further salts.

In one embodiment of the present invention, aqueous solution of transition metal salts may comprise one or more additives which may be selected from biocides, complexing agents, for example ammonia, chelating agents, surfactants, reducing agents, carboxylic acids and buffers. In another embodiment of the present invention, aqueous solution of transition metal salts does not comprise any additives.

Examples of suitable reducing agents which may be in aqueous solution of transition metal salts are sulfites, especially sodium sulfite, sodium hydrogensulfite, potassium sulfite, potassium bisulfite, ammonium sulfite, and also hydrazine and salts of hydrazine, for example the hydrogensulfate, and also water-soluble organic reducing agents, for example ascorbic acid or aldehydes.

According to the invention, aqueous solution of transition metals is combined with at least one solution of at least one carbonate or hydrogencarbonate of at least one alkali metal which may comprise hydroxide.

In one embodiment of the present invention, aqueous solution of transition metals is combined with aqueous solution of at least one alkali metal hydrogencarbonate or preferably of at least one alkali metal carbonate or alkali metal hydroxide, for example by addition of solution of alkali metal (hydrogen)carbonate to aqueous solution of transition metal salts. Particularly preferred alkali metal carbonates are sodium carbonate and potassium carbonate, and also ammonium carbonate. Particularly preferred alkali metal hydrogencarbonates are potassium hydrogencarbonate and ammonium hydrogencarbonate. Particularly preferred alkali metal hydroxides are sodium hydroxide and potassium hydroxide.

The combination brings about precipitation of transition metal hydroxide or transition metal carbonate or mixed carbonates and hydroxides of transition metals.

In one embodiment of the present invention, the precipitation is brought about by addition of an aqueous solution of sodium carbonate or potassium carbonate to an aqueous solution of acetates, sulfates or nitrates of transition metals.

Aqueous solution of alkali metal (hydrogen)carbonate may have a concentration of carbonate in the range from 0.1 to 3 mol/l, preferably 1 to 2.5 mol/l. It may also comprise hydrogencarbonate. It may also comprise hydroxide.

Aqueous solution of alkali metal (hydrogen)carbonate or alkali metal hydroxide may comprise one or more further salts, for example ammonium salts, especially ammonium hydroxide, ammonium sulfate or ammonium sulfite. In one embodiment, a molar NH₃: transition metal ratio of 0.01 to 0.9, more preferably 0.02 to 0.2, can be established.

The combination can be executed in one or more steps, in each case continuously or batchwise. For instance, solution of alkali metal (hydrogen)carbonate or alkali metal hydroxide can be fed into the stirred vessel via one or more feed points, in such a way that the respective feed point is above or below the liquid level. More particularly, it is possible to meter exactly into the vortex in a stirred tank produced by the stirrer. For instance, it is additionally possible to meter aqueous solution of transition metal salts into the stirred vessel via one or more feed points, in such a way that the respective feed point is above or below the liquid level. More particularly, it is possible to meter exactly into the vortex in a stirred tank produced by the stirrer.

In one embodiment of the present invention, the procedure is to feed an aqueous solution of alkali metal (hydrogen)carbonate into a stirred vessel with at least two aqueous solutions each of one transition metal salt via separate feed points in each case. In another embodiment of the present invention, the combination is performed by feeding an aqueous solution of an alkali metal (hydrogen)carbonate into a stirred vessel with an aqueous solution comprising all transition metals desired for performance of the process according to the invention as salts, via separate feed points in each case. The latter procedure has the advantage that inhomogeneities in the concentration ratios of the different transition metals can be more easily avoided.

The combination of aqueous solution of transition metal salts with at least one solution of alkali metal (hydrogen)carbonate or alkali metal hydroxide produces an aqueous suspension of transition metal carbonate, since transition metal carbonate precipitates out. The aqueous continuous phase, which is also called mother liquor in the context of the present invention, comprises water-soluble salts and possibly further additives present in solution. Examples of possible water-soluble salts include alkali metal salts of the anions of transition metal salts used, for example sodium acetate, potassium acetate, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, sodium halide, potassium halide, including the corresponding ammonium salts, for example ammonium nitrate, ammonium sulfate and/or ammonium halide. The mother liquor most preferably comprises sodium chloride, potassium chloride or ammonium chloride. In addition, mother liquor may comprise additional salts, optionally used additives and optionally excess alkali metal (hydrogen)carbonate or alkali metal hydroxide, and also unprecipitated transition metal as transition metal salt.

The pH of the mother liquor is preferably in the range from 7 to 10, more preferably in the range from 7.5 to 9.0.

During the reaction, a stirrer power of at least 0.25 W/l is introduced, preferably at least 2 W/l and more preferably at least 5 W/l. The introduction of stirrer power can be accomplished, for example, in a stirred vessel by means of one or more stirrers or in a separate compartment. Examples of suitable stirrers are anchor stirrers, blade stirrers, especially pitched-blade stirrers, and also propeller stirrers, disk stirrers and turbine stirrers.

In one embodiment of the present invention, a stirrer power of up to 50 W/l is introduced.

In one embodiment of the present invention, moving stirrers, for example blade stirrers or pitched-blade stirrers, are combined with static stirrers, for example baffles.

In one variant of the present invention, it is possible to introduce further mechanical energy at least partly by means of ultrasound. In another variant, no further mechanical energy is introduced by ultrasound.

In one variant of the present invention, in at least one further compartment, a mechanical power in the range from 50 to 10 000 W/l, preferably 200 to 2500 W/l, more preferably to 500 W/l (watts per liter), based on the proportion of the suspension, can be introduced continuously in a proportion of the suspension in each case, and then the proportion can be returned to the stirred vessel.

The further compartment selected may comprise pumps, inserts, mixing units, wet mills, homogenizers and stirred tanks, and stirred tanks selected as the further compartment preferably have a much smaller volume than the stirred vessel described at the outset. The further compartment preferably has a volume in the range from 0.01 to 20% by volume of the stirred vessel described at the outset.

Examples of particularly suitable pumps are centrifugal pumps and peripheral wheel pumps.

The further compartment used may be a separate vessel or an insert into the stirred vessel. Inserts are understood to mean those plant parts which are within the volume of the actual stirred vessel but are isolated by construction means and have a dedicated mixing unit. For example, the insert selected may be a tube which is immersed into the stirred vessel and the reaction mixture and is mixed with the aid of a further stirrer, for example a stirrer with propellers. This creates a compartment in the stirred vessel. The proportion of the compartment volume to the total volume is 0.1 to 20% by volume, preferably 0.1 to 10% by volume. In one variant, several such compartments may be present, which may be of the same or different sizes.

During the admixing with alkali metal (hydrogen)carbonate or alkali metal hydroxide, the reaction volume is kept essentially constant by removing liquid phase while adding solution of alkali metal (hydrogen)carbonate. In the course of this, precipitated mixed carbonate or hydroxide of at least two transition metals is left completely or essentially in the reaction vessel, preferably in a stirred vessel.

The removal can be performed, for example, as a distillative removal or preferably as a solid/liquid separation, for example by decanting off with the aid of an overflow or by means of a hydrocyclone or by means of lamellar clarifying apparatus(es), countercurrent classifiers or combinations of at least two of the aforementioned apparatuses.

In one embodiment of the present invention, the process according to the invention is performed in a stirred vessel to which a pumped circulation system is attached, to which an apparatus for solid/liquid separation is attached. In another embodiment of the present invention, two or more separate vessels attached to the stirred vessel are connected to the stirred vessel via one or more pumped circulation systems. Apparatuses for solid/liquid separation may then be connected to the separate vessels.

A “pumped circulation system” is preferably understood to mean an apparatus which continuously removes a portion of the reactor contents from the reactor, supplies it to a separate vessel and, after flow through the separate vessel, returns it to the reactor. To maintain the flow, a pump is used. In a particular embodiment, devices present in the separate vessel may have pumping action, such that it is possible to work without a separate pump unit.

In one embodiment of the present invention, the process according to the invention can be performed at a temperature in the range from 40 to 80° C., preferably 45 to 60° C. The temperature is determined in the stirred vessel. The temperature in further compartments or in the pump circulation system may differ from the temperature in the stirred vessel.

The process according to the invention can be performed under air, under inert gas atmosphere, for example under noble gas or nitrogen atmosphere, or under reducing atmosphere. Examples of reducing gases include, for example, CO and SO₂. Preference is given to working under inert gas atmosphere.

The process according to the invention can be performed at any pressure, provided that the pressure is not below the vapor pressure of the aqueous solution or suspension. For example, 1 to 10 bar is suitable, preference being given to standard pressure.

In one embodiment of the present invention, a mean solids content in the range from 70 to 1000 g/l, determined in the stirred vessel, is employed, preferably 300 to 700 g/l.

In one embodiment of the present invention, a reaction time in the range from 2 to 50 hours is employed, preferably 4 to 20 hours.

In one embodiment of the present invention, on commencement of the reaction (precipitation), nuclei (seed crystals) for transition metal carbonate can be added, for example aqueous suspension containing 30 to 150 g/l, preferably about 90 g/l, of seed crystals.

Mixed carbonates and/or hydroxides of at least two transition metals prepared by the process according to the invention are obtained with very good morphology. For instance, it has a mean particle diameter (D50) in the range from 6 to 16 μm, especially 7 to 9 μm. The mean particle diameter (D50) in the context of the present invention refers to the median of the volume-based particle diameter, as can be determined, for example, by light scattering.

After the precipitation, further steps can be performed, for example removal of the precipitated mixed carbonate and/or hydroxide of transition metals, and also drying or classifying.

The removal can be effected, for example, by filtration, centrifugation, decantation, spray drying or sedimentation, or by a combination of two or more of the aforementioned operations. Examples of suitable apparatus include filter presses, belt filters, hydrocyclones, lamellar clarifying apparatuses, countercurrent classifiers or combinations of the aforementioned apparatuses.

The removal may be followed, especially when the removal is performed by filtration, by one or more wash steps. It is possible, for example, to wash with pure water or with an aqueous solution of alkali metal carbonate or alkali metal hydroxide, especially with an aqueous solution of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonia. Water is preferred.

Wash step(s) can be effected, for example, with employment of elevated pressure or elevated temperature, for example 30 to 50° C. In another variant, wash step(s) is/are performed at room temperature.

The efficiency of the wash steps can be checked by analytical measures. For example, the content of transition metals M in the wash water can be analyzed.

In the case that washing is effected with water rather than with an aqueous solution of alkali metal carbonate, it is possible with the aid of conductivity tests on the washing water to check whether water-soluble substances, for example water-soluble salts, can be washed out.

The removal may be followed by one or more drying steps. Drying step(s) can be performed at room temperature or at elevated temperature. For example, it is possible to dry at temperatures in the range from 30 to 150° C.

Drying step(s) can be performed at standard pressure or under reduced pressure, for example at a pressure in the range from 10 mbar to 500 mbar.

In one embodiment of the present invention, precursors produced by the process according to the invention still comprise physically bound water even after any drying step(s).

In one embodiment of the present invention, the removal is followed by one or more wash steps and optionally one or more drying steps.

The water content and particle diameter of precursor of mixed transition metal oxide are determined after the removal of the mother liquor, preferably after the drying.

In one embodiment of the present invention, particles of transition metal carbonate which have a diameter of more than 20 μm are removed, for example by sieving. If sieving is desired, the sieving is preferably conducted after the drying. Preference is given to removing particles of transition metal carbonate which have a diameter of more than 32 μm, more preferably more than 50 μm.

In one embodiment of the present invention, the tamped density of transition metal carbonate prepared in accordance with the invention is in the range from 1.3 to 2.4 g/cm³, preferably 1.7 to 2.2 g/cm³. The tamped density can be determined, for example, essentially to DIN 53194 or DIN ISO 787-11, but advantageously with not more than 1250 taps and with smaller cylinders.

The process according to the invention affords mixed carbonates and/or hydroxides of at least two transition metals in particulate form, also called precursor or transition metal carbonates for short. Transition metal carbonates prepared by the process according to the invention are very suitable for production of electrode materials for cathodes for lithium ion batteries, for example by mixing transition metal carbonate prepared by the process according to the invention with one or more lithium compounds and thermally treating it at one or more temperatures in the range from 300 to 1000° C., preferably 500 to 900° C., over a period of 1 to 24 hours. Cathode materials produced using transition metal carbonates prepared in accordance with the invention are notable for advantageous morphology and high tamped density. They also feature a high energy density.

The invention is illustrated in detail by examples.

General preliminary remarks: for all examples and the comparative example, a stirred tank having a volume of 6 liters was used, which had a pumped circulation system having a capacity of 1.8 liters and a sedimenter and a centrifugal pump having a total power of 45 W and a power density of 400 W/l in the pump head. The stirred tank had two pitched-blade stirrers.

During the reaction (precipitation), a nitrogen stream of 40 l/h was introduced into the gas space of the stirred tank, in such a way that the nitrogen stream was introduced above the liquid phase.

For the experiments, the following solutions were always used, unless explicitly stated otherwise.

Solution A: Aqueous solution of 0.363 mol/l NiSO₄, 0.198 mol/l CoSO₄ and 1.098 mol/l MnSO₄.

Solution B: Aqueous solution of 1.5 mol/l Na₂CO₃, 0.046 mol/l NH₄HCO₃ and 0.029 mol/l (NH₄)₂SO₃.

I Preparation of Transition Metal Carbonates

I.1 Comparative Example: Preparation of Comparative Product CP-1

The above-described 6 l stirred tank with pumped circulation system was initially charged with 4 liters of water. It was heated to 55° C. while stirring.

Then, while stirring continuously, solution A was metered in simultaneously and homogeneously at a rate of 780 g/h, and solution B at a rate of 838 g/h. A mixed Ni/Co/Mn carbonate hydroxide precipitated out. The stirring speed was increased continuously from 100 revolutions/min (“rpm”) to 630 rpm.

After 2 hours 48 minutes, the maximum permissible fill level had been attained, and the metered addition of solutions A and B was ended. The mixture was stirred at 55° C. for a further 3 hours. The stirred tank comprised about 54 g/l of mixed Ni/Co/Mn carbonate hydroxide. The resulting transition metal carbonate was removed by means of a suction filter, washed with 25 l of distilled water and dried at 90° C. in a drying cabinet for 18 hours. The mixture was sieved with a 50 μm mesh sieve, and oversize having a secondary particle diameter of more than 50 μm was removed. This gave comparative product CP-1.

Analytical data can be found in table 1.

I.2 Inventive Preparation of Transition Metal Carbonate P-1

The above-described 6 l stirred tank with pumped circulation system was initially charged with 5 liters of water. It was heated to 55° C. while stirring.

Then, while stirring continuously, solution A was metered in simultaneously and homogeneously at a rate of 772 g/h, and solution B at a rate of 836 g/h. A mixed Ni/Co/Mn carbonate hydroxide precipitated out. The stirring speed was increased continuously from 100 rpm to 600 rpm.

Once the fill level of the stirred tank with pumped circulation system had attained a fill level of 7.7 liters, the sedimenter was switched on. The sedimenter was used to draw off about 1.6 liters of mother liquor per hour without drawing off significant amounts of solids.

After 18 hours, the metered addition of solutions A and B was ended. The mixture was stirred at 55° C. and 220 rpm for a further 3 hours. The stirred tank comprised 330 g/l of transition metal carbonate. The transition metal carbonate obtained was removed by means of a suction filter, washed with 25 l of distilled water and dried at 90° C. in a drying cabinet for 18 hours. Oversize having a secondary particle diameter of more than 50 μm was removed by sieving (mesh 50 μm).

Product P-1 obtained in accordance with the invention was obtained.

Analytical data can be found in table 1.

I.3 Inventive Preparation of Transition Metal Carbonate P-2

The above-described 6 l stirred tank with pumped circulation system was initially charged with 5 liters of water. It was heated to 55° C. while stirring.

Then, while stirring continuously, solution A was metered in simultaneously and homogeneously at a rate of 876 g/h, and solution B at a rate of 947 g/h. A transition metal carbonate precipitated out. The stirring speed was increased continuously from 100 rpm to 475 rpm.

Once the fill level of the stirred tank with pumped circulation system had attained a fill level of 7.7 liters, the sedimenter was switched on. The sedimenter was used to draw off about 1.8 liters of mother liquor per hour without drawing off significant amounts of solids.

After 18 hours, the metered addition of solutions A and B was ended. The mixture was stirred at 55° C. and 250 rpm for a further 3 hours. The stirred tank comprised 633 g/l of transition metal carbonate. The transition metal carbonate obtained was removed by means of a suction filter, washed with 25 l of distilled water and dried at 90° C. in a drying cabinet for 18 hours. Agglomerates having a secondary particle diameter of more than 50 μm were removed by sieving.

Product P-2 obtained in accordance with the invention was obtained. Analytical data can be found in table 1.

I.4 Inventive Preparation of Transition Metal Carbonate P-3

A 6 l stirred tank without pump circulation system was initially charged with 1.1 liters of water. It was heated to 55° C. while stirring (350 rpm). 3.34 kg of solution A and 3.61 kg of solution B were metered in simultaneously and homogeneously within 3 hours 48 minutes. This gave 6.8 l of suspension of mixed Ni/Co/Mn carbonate hydroxide, (D50): 7.3 μm.

2.83 l of the suspension thus prepared were initially charged in the above-described 6 l stirred tank with pump circulation system and heated to 55° C. while stirring. Then solution A was metered in simultaneously and homogeneously at a rate of 1.49 kg/h, and solution B at a rate of 1.60 kg/h, while stirring continuously. A mixed Ni/Co/Mn carbonate precipitated out. The stirrer speed was increased continuously from 250 revolutions/min (“rpm”) to 475 rpm.

Once the fill level of the stirred tank with pumped circulation system had attained a fill level of 7.7 liters, the sedimenter was switched on. The sedimenter was used to draw off about 3.1 liters of mother liquor per hour without drawing off significant amounts of solids.

After 14.5 hours, the metered addition of solutions A and B was ended. The mixture was stirred at 55° C. and 250 rpm for a further 3 hours. The stirred tank comprised 566 g/l of transition metal carbonate. The transition metal carbonate obtained was removed by means of a suction filter, washed with 25 l of distilled water and dried at 90° C. in a drying cabinet for 18 hours. Oversize having a secondary particle diameter of more than 50 μm was removed by sieving (mesh 50 μm).

Product P-3 obtained in accordance with the invention was obtained.

Analytical data can be found in table 1.

TABLE 1 Analytical data of transition metal carbonates obtained in accordance with the invention and comparative products. Tamped density Example No. Ni Co Mn C D50 [μm] [g/ml] C-P1 10.8 5.9 30 8.5 4.5 1.09 P-1  10.3 5.7 28.7 8.9 6.7 1.51 P-2  9.5 6 31 9.2 7.4 1.68 P-3  9.8 5.7 28 8.7 11.1 1.67 Figures for Ni, Co, Mn and C (from carbonate) each in g/100 g.

II. General Procedure for Preparation of Mixed Transition Metal Oxides

For preparation of inventive materials, a transition metal carbonate according to table 1 was mixed with Li₂CO₃ with a selected molar ratio of Li: (Ni+Co+Mn) of 1.5. The mixture thus obtainable was transferred into an alumina crucible. It was calcined in a muffle furnace by heating at a heating rate of 3 K/min and including hold times of 4 hours each on attainment of 350° C. and 650° C. before increasing the temperature further. Calcination was effected at a calcination temperature of 850° C. over a period of a further six hours, followed by cooling at a rate of 3° C./min. This gave inventive cathode materials CM-1 to CM-3 and comparative cathode material C-CM.

The tamped density of the cathode materials produced was determined.

TABLE 1 Analytical data of cathode materials produced from transition metal carbonates obtained in accordance with the invention or comparative products Transition Cathode material Cathode metal tamped density material carbonate (kg/l) C-CM C-P1 1.32 CM-1 P-1 1.98 CM-2 P-2 1.93 CM-3 P-3 1.78 

1. A process for batchwise preparation of carbonates of at least two transition metals which may comprise hydroxide(s) of the corresponding transition metals, which comprises combining at least one aqueous solution comprising at least two transition metal salts having cations of at least two different transition metals overall with at least one solution of at least one carbonate or hydrogencarbonate of at least one alkali metal or ammonium, introducing a stirrer power of at least 0.25 W/l, and keeping the reaction volume essentially constant during the admixing with alkali metal (hydrogen)carbonate by removing liquid phase while adding solution of alkali metal (hydrogen)carbonate or alkali metal hydroxide.
 2. The process according to claim 1, which is performed in the presence of at least one complexing agent other than water.
 3. The process according to claim 1 or 2, which is performed for at least some of the time at a solids concentration of at least 500 g/l.
 4. The process according to any of claims 1 to 3, wherein the reactor system selected is a reaction vessel having at least one apparatus by which solid/liquid separations can be conducted.
 5. The process according to claim 4, wherein the apparatus by which solid/liquid separations can be conducted is selected from sedimenters, lamellar clarifiers, centrifuges and units for inverse filtrations.
 6. The process according to any of claims 1 to 5, wherein the reactor system selected is a tank having a pumped circulation system.
 7. The process according to any of claims 1 to 6, wherein the actual precipitation is performed at a reaction temperature in the range from 40 to 80° C.
 8. The process according to any of claims 1 to 7, wherein aqueous solution comprising at least three transition metal salts having cations of at least three different transition metals is used.
 9. The process according to any of claims 1 to 8, wherein aqueous solution of salts of nickel, cobalt and manganese is used.
 10. The process according to any of claims 1 to 9, wherein seed crystals or crystallization nuclei are added at the start of the reaction.
 11. The process according to any of claims 1 to 10, wherein carbonates of at least two transition metals which may comprise hydroxide(s) of the corresponding transition metals comprise 0.01 to 45 mol % of anions other than carbonate ions, based on the total number anions in the transition metal carbonate in question. 